1. Field of the Invention
This invention relates to a method and apparatus for charging electric devices. More particularly, the present invention relates to a system for powering an electric vehicle that protects against lightening strikes and electrical surges.
2. Description of the Background Art
The use of electrically powered vehicle is known in the art. For example, U.S. Pat. No. 3,637,956 to Blackman discloses an electrical automobile transportation system. The system embodies exposed electrified conductors on the road and electrical current collectors on the vehicle for contacting the road conductors. The electrified conductors supply electrical energy to the vehicle for power.
Another example is U.S. Pat. No. 3,914,562 to Bolger. Bolger discloses an electrically driven vehicle that has suitable batteries to drive the vehicle on conventional roads. The vehicle also has means for receiving power from a conductor embedded in a prepared roadway for driving the vehicle and for charging the batteries.
Another electric vehicle is disclosed in U.S. Pat. No. 4,139,071 to Tackett. Tackett discloses a roadway having a smooth road surface for vehicles and means for transmitting electric current through the road surface to electrically operated vehicles traveling thereon.
Lightning poses a serious problem in all of the referenced systems. Indeed, the damaging effect of a lightening strike, or other power surge, is a major obstacle for any electrically powered vehicle that receives power from either an overhead electric cable or from an electrified rails. If a strong lightning bolt strikes a power supply cable or rail the electric surge can travel for miles and cause damage to both the attached vehicles and to the system of transformers that power the distribution lines.
A continuous electric rail carrying a high charge is an attractive target for lightning. However, by creating intermittent charging stations along a roadway instead of having a continuous electric rail the probability of lightning damage is reduced in proportion to the length of the rail segments.
This is a result of the fact that each unit length of exposed, charged rail has an equal opportunity of being struck by lightning. If, for example, a 5 ft. long rail segment replaces a 10 mile long powered rail then the probability of a lightning strike has been reduced 10,560 times (i.e. 5 ft. divided by 52,800 ft.) This takes place just by using an intermittent rail.
An additional safety measure not present in the referenced inventions is the use of an electrical circuit that is partially opened during the charging process. Namely, the circuit between the vehicle's batteries and the vehicle's capacitors are left opened while the capacitor is charging. This minimizes damage to the charging station and/or vehicle in the event of a lightning strike. Namely, the on board batteries are not charging while the on board capacitors have a direct charging circuit connection with the underlying rail segment.
Accordingly, although each of the referenced inventions achieves its own unique objective, all suffer from common drawbacks. Namely, the use of continuous electrical rails dramatically increases the possibility of damage from lightening strikes. Moreover, if struck, the severity of the resulting damage is far greater. Yet another problem associated with electric powered vehicles is the cost of providing a continuous set of electrified rails along every foot of the roadway. Continuous electrified rails consume large amounts of energy and are inefficient. The present invention is aimed at overcoming these deficiencies.